It is common for electronic linear digital measuring systems which use capacitive technology to use a sensor strip with a repeating metallic pattern to provide the feedback signal to the readout. This sensor strip is typically made from an FR4 fiberglass material which has a copper or other metallic film deposited on the surface. This metallic surface is then accurately etched to provide the proper pattern for processing the measurement signal.
The FR4 type of material is preferred because of its stable characteristics in regards to temperature, humidity and physical handling. The drawback of using this material is that it is currently only manufactured in short lengths of about 48″ long. This limits the maximum length to be measured to something less than 48″. It is possible to carefully connect several pieces of this material to make longer systems; however, presently this connection must be down at the factory level using complex and time consuming methods to insure the accuracy.